86 lines
3 KiB
Java
86 lines
3 KiB
Java
import java.time.Month;
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import java.util.Collection;
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import java.util.List;
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import java.util.Set;
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import java.util.stream.Collectors;
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public class Main {
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private static class Birthday {
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private Month month;
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private int day;
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public Birthday(Month month, int day) {
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this.month = month;
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this.day = day;
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}
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public Month getMonth() {
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return month;
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}
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public int getDay() {
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return day;
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}
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@Override
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public String toString() {
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return month + " " + day;
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}
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}
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public static void main(String[] args) {
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List<Birthday> choices = List.of(
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new Birthday(Month.MAY, 15),
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new Birthday(Month.MAY, 16),
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new Birthday(Month.MAY, 19),
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new Birthday(Month.JUNE, 17),
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new Birthday(Month.JUNE, 18),
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new Birthday(Month.JULY, 14),
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new Birthday(Month.JULY, 16),
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new Birthday(Month.AUGUST, 14),
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new Birthday(Month.AUGUST, 15),
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new Birthday(Month.AUGUST, 17)
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);
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System.out.printf("There are %d candidates remaining.\n", choices.size());
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// The month cannot have a unique day because Albert knows the month, and knows that Bernard does not know the answer
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Set<Month> uniqueMonths = choices.stream()
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.collect(Collectors.groupingBy(Birthday::getDay))
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.values()
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.stream()
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.filter(g -> g.size() == 1)
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.flatMap(Collection::stream)
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.map(Birthday::getMonth)
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.collect(Collectors.toSet());
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List<Birthday> f1List = choices.stream()
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.filter(birthday -> !uniqueMonths.contains(birthday.month))
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.collect(Collectors.toList());
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System.out.printf("There are %d candidates remaining.\n", f1List.size());
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// Bernard now knows the answer, so the day must be unique within the remaining choices
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List<Birthday> f2List = f1List.stream()
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.collect(Collectors.groupingBy(Birthday::getDay))
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.values()
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.stream()
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.filter(g -> g.size() == 1)
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.flatMap(Collection::stream)
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.collect(Collectors.toList());
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System.out.printf("There are %d candidates remaining.\n", f2List.size());
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// Albert knows the answer too, so the month must be unique within the remaining choices
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List<Birthday> f3List = f2List.stream()
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.collect(Collectors.groupingBy(Birthday::getMonth))
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.values()
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.stream()
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.filter(g -> g.size() == 1)
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.flatMap(Collection::stream)
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.collect(Collectors.toList());
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System.out.printf("There are %d candidates remaining.\n", f3List.size());
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if (f3List.size() == 1) {
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System.out.printf("Cheryl's birthday is %s\n", f3List.get(0));
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} else {
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System.out.println("No unique choice found");
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}
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}
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}
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